The first "passive house" in Fairfax County, now under construction in Falls Church, is super insulated, airtight and is expected to save its owners 90 percent on annual energy costs. (Tom Jackman/The Washington Post)

A “passive house” uses 90 percent less energy than conventional houses, in part by using heavy insulation and airtight seals to maintain internal temperature without the external fluctuations of silly things like “seasons” and ”extreme weather.” The first one in Northern Virginia was built in Arlington, and now Nelson and Caroline Labbe are building one in the Pimmit Hills neighborhood of Fairfax County, with the help of architect Peter Henry and builder Richard Dobson.

Inside the passive house in Pimmit Hills: Builder Richard Dobson, owner Nelson Labbe, architect Peter Henry and project manager Eric Kluge. (Tom Jackman/The Washington Post)

The first passive homes were built in Germany in 1990, and there are thought to be about 20,000 “passivhaus” units in the world, mostly in Europe. In the D.C, area, there are four: One in Arlington, one in Bethesda and one in Northeast Washington that was a State University of New York joint New School and Stevens Institute of Technology student project for the Energy Department’s biennial Solar Decathlon on the Mall.

By insulating and sealing the house, it becomes much more energy efficient by not having to heat or cool itself to contend with the exterior elements. In Pimmit Hills, the Labbes’ house not only has insulation under the slab, but two feet of insulation in the attic, and two inches of foam insulation on the exterior walls, which are already 9 1/2 inches thick. The insulation is also treated to fend off termites and permit drainage.

Below the concrete slab in the basement of the passive house is a 6-inch layer of foam insulation. And then the metal footer is also surrounded by insulation. (Tom Jackman/The Washington Post)

“We’ve been building houses the same way for 150 years,” Henry said, from the days of wood-burning heat stoves to central air and heat furnaces. “There hasn’t been much thinking about thermal efficiency.”

Labbe, who works for the U.S. Army Corps of Engineers, said his colleagues work on energy conservation, and it convinced him and his wife they wanted to build an energy efficient house. “We learned about passive houses,” Labbe said, “and we thought, ‘that’s it.’”

An active kayaker, Labbe mentioned his interest in a passive house to another kayaker, Henry, not knowing Henry was an environmentally involved architect. Henry took training from the Passive House Institute U.S. and worked with the Labbes within their budget.

The Labbes found a bank willing to finance them, Sandy Spring Bank, on their second try. “We explained it to them, and they said OK,” Labbe said.

In addition to thick foam insulation on the exterior of the house, a second layer of insulation allows water to drain away from the walls. (Tom Jackman/The Washington Post)

Eric Kluge, the project manager, said the Pimmit Hills house will be a helpful experience. If they do another passive house, “our efficiency’s going to pick up,” Kluge said.

The passive house will use no gas or any combustion devices, which require outside ventilation. Instead, all the ventilation is controlled and 90 percent of the air that passes through the house will be recycled through an Energy Recovery Ventilator, Henry said. Two “mini-split” units, small self-contained devices, will heat and cool the air without taking up the room of a central furnace.

Vapor barriers are built in to keep moisture from building up inside, and the mini-split units can also function as dehumidifiers, Henry said. Water will be heated with a heat pump. The stove will be a low-energy induction stove. All lights will be LED or CFL.

The annual energy costs for the house should drop from about $2,000 for a 3,000-square foot to about $200 a year, Labbe estimated.

Thick sheets of dense styrofoam insulation cover the exterior of the house, and will soon be covered by siding. (Tom Jackman/The Washington Post)

“The architect had a really great design,” Lensis said. “They took special care to seal the envelope up, and the builder did a fantastic job.”

But he cautioned that the task isn’t completed. Now that electrical and plumbing contractors have been in, drilling their holes in the house, a second test will be run before siding and other permanent external touches are applied. Then, a third test will be done after the house is finished for final certification.

Construction started in May, and Dobson said he hopes to be done by late January or early February. The house is larger than most in the Pimmit Hills neighborhood, but not conspicuously so. If the house is certified, Labbe said he will allow tours from around the world to inspect his working passive house.

CORRECTION: One of the existing passive houses in our area was originally misidentified as being constructed by students from the State University of New York. It was built by students in a joint project between The New School of New York and Stevens Institute of Technology in Hoboken, N.J.